1. Field of the Invention
This invention relates to a spread spectrum wireless telephone system.
2. Description of Related Art
Access to telephone networks, may commonly occur via one of two general mechanisms, termed xe2x80x9cprivate accessxe2x80x9d and xe2x80x9cpublic accessxe2x80x9d. As used herein, xe2x80x9cprivate accessxe2x80x9d means access by means of dedicated circuits (and includes business telephones through PBX, Centrex, and key-type systems, and home telephones), while xe2x80x9cpublic accessxe2x80x9d means access by means of common communication channels (and includes cellular telephones and payphones). Interconnection to a public switched telephone network (PSTN) for both private access and public access may make use of cable, fiber optic, wire, or radio frequency links, or other methods of communication known in the art. Many telephone networks, have a large number of telephones which are hardwired into the network and which have private access to the network from fixed locations.
One problem which has arisen in the art is the desire of mobile persons to have convenient and inexpensive access to telephone networks. These persons generally have a choice between locating a private-access business or home telephone, or a public-access payphone, which can be inconvenient, and using cellular telephone service, which can be expensive. Accordingly, it would be advantageous to provide a relatively convenient and inexpensive system which allows public access to telephone networks.
Moreover, public access to telephone networks is subject to a number of problems, due in part to the public nature of the communication channel. Such communication may be subject to eavesdropping and other security risks, and may also be subject to unpredictable loss, noise, interference, and even active jamming. Many of these problems are ameliorated by spread-spectrum radio communication, in which transmitted signals are spread across a bandwidth which is wider than the bandwidth of the signal. Spread-spectrum communication may also be used in conjunction with CDMA, FDMA, TDMA, and other multiplexing techniques, and thus may offer advantages in a switching network.
One method of public access to telephone networks is shown in U.S. Pat. No. 4,878,238. While the system shown therein may achieve the goal of public access to a telephone network, it is subject to the drawback that it is not able to achieve the advantages of spread-spectrum communication. Moreover, the system shown therein has little or no ability to handoff user stations from one base station to another when conditions warrant. It would be advantageous to allow public access to the telephone network with relatively inexpensive user stations and which achieve this and other advantages of spread-spectrum communication.
Some aspects of the art of spread spectrum wireless communication are shown in U.S. Pat. Nos. 5,016,255 (issued May 14, 1991) and 5,022,047 (issued Jun. 4, 1991), and in the following copending applications: Ser. No. 07/682,050, filed Apr. 8, 1991, in the name of inventor Robert C. Dixon, titled xe2x80x9cTHREE-CELL WIRELESS COMMUNICATION SYSTEMxe2x80x9d, and Ser. No. 07/600,772, filed Oct. 23, 1990, in the name of inventors Robert C. Dixon and Jeffrey S. Vanderpool, titled xe2x80x9cMETHOD AND APPARATUS FOR ESTABLISHING SPREAD SPECTRUM COMMUNICATIONSxe2x80x9d. Each of these patents and applications is hereby incorporated by reference as if fully set forth herein.
Another aspect of the problem of access to telephone networks is the desire for mobile persons to be able to contact each other, for example, when these persons are closely located. Access by each such person to a telephone network would allow for them to contact each other, but it might place excess burden on the telephone network and might result in unwarranted delays in making such contacts. Accordingly, it would be advantageous to provide a relatively convenient and inexpensive system which allows contact between multiple user stations which have access (either private or public) to telephone networks.
One method of wireless contact between a plurality of user stations is shown in U.S. Pat. No. 4,672,658. While the system shown therein may achieve the goal of operating a wireless PBX, it is subject to the drawback that it may require complex and relatively expensive user stations, and may not be smoothly integrated into a system for access to telephone networks. Accordingly, it would be advantageous to provide private exchange telephone systems (including PBX, Centrex, or key-type systems) which can be smoothly integrated in a system for providing access (either private or public) to telephone networks with relatively inexpensive user stations.
Another development in the art of telephone networks is the xe2x80x9cintelligent networkxe2x80x9d, used herein to mean a telephone network in which enhanced telephone network services are performed by an independent processor, rather than by a local switch or a local switching processor. In an intelligent network, a telephone caller can communicate directly with the independent processor, for controlling enhanced telephone network features. Examples of these enhanced features are call routing and call screening.
Some of these enhanced features are useful for rerouting messages from one telephone to another, while others are useful for caching messages while a person is not available at a particular telephone. Both of these purposes are quite suited to mobile persons who frequently access telephone networks. Moreover, enhanced features add to the value of having a telephone and thus encourage mobile persons to use mobile telephones. Accordingly, it would be advantageous if enhanced features were available to mobile telephones.
The invention provides a system for accessing a telephone system, in which a set of user stations are matched with a set of base stations for connection to a telephone network. Base stations may be coupled directly or indirectly to the telephone network and may be capable of initiating or receiving calls on the telephone network. User stations may be mobile, may comprise a spread-spectrum transmitter or receiver and may be capable of dynamic connection to selected base stations. A plurality of base stations may be coupled to a private exchange telephone system for coupling user stations in calls outside the telephone network.
In embodiments of the invention, user stations may use CDMA, FDMA, TDMA or other multiple-access techniques to obtain one or more clear communication paths to base stations. Base stations may be placed at convenient locations or may themselves be mobile. User stations may make and break connections with base stations as the user station moves between service regions, or is otherwise more advantageously serviced by, base stations. User stations may direct requests to and receive information from an enhanced telephone services processor, so as to obtain enhanced telephone services within the telephone network. Base stations may be coupled to each other by means of a private exchange telephone system or other small business telephone system (such as a PBX, Centrex, or key-type system) so as to couple user stations in calls outside the telephone network. User stations may also be coupled directly or indirectly to the telephone network on their own or by another access path, such as narrowband or spread-spectrum cellular telephone circuits.